由土壤化育特徵探討珊瑚礁 海階面之地表作用 以恆春西台地為例

Abstract

Coastal landscapes undergo complex and rapidly changing geomorphic processes. Geomorphic processes and changes can be revealed by proxies of pedogenic features of soils overlaying the coastal reef-terraces. This study investigated and analyzed four soils (HT-1a-1d) on the highest reef-terraces of the West Hengchun Hills. Based on the micromorphologic profiles of four soils, this study identified features of the argillic horizon and higher rubifications. Two of the four soils (HT-1b and 1d) revealed poly-sequences indicated that they had been covered by re-depositional material eroded from the higher soils. Further analyses revealed high and similar pedogenicity of these four soils. Furthermore, properties of the soils suggest higher and similar pedogenic degrees. For example, the clay content in the Bt horizons of the soils was 33-40%, and the pH values were 5 to 7. Although the base saturation percentage exceeded 70% due to high Ca and Mg content, the cation exchangeable capacity (CEC) of the four soils was less than 10 cmol (+) kg^(-1). DCB extracted Fe in the Bt horizons of the soils were 25-28 g kg^(-1), but oxalate-oxalic acid extracted Fe were lower. The XRD revealed high amounts of kaolinite in the Bt horizons of the four soils. The soils could be classified as Typic Paleudults according to the Soil Taxonomy. The Simonsen model was used to analyze the pedogenic processes of the soils. Finally, based on the pedogenic processes and the parent materials of the four soils reported in an early study, a soil-geomorphic process model was developed for gauging the landform-surface evolution of the higher reef-terraces in the West Hengchun Hills.